Rotation of Crops. 
613 
The Dry Matter in the Barley Crops . — The second division of 
Table Y. compares the amounts of dry matter yielded in barley, 
grown, respectively, in rotation, and continuously — that is, year 
after year on the same land. The results for the continuously 
grown crops relate to the average produce ofthe same eightseasons 
as those in which the rotation crops were obtained. The unmanured 
and the superphosphate conditions were also quite parallel in 
the two series of experiments. In the case ofthe mixed manure 
resalts, it should be borne in mind that in the rotation experi- 
ments a quantity of manure was applied for the preceding crop — 
the turnips — which is supposed to carry the whole of the crops of 
the four years’ course ; whilst, in the continuous experiments, 
the quantity of nitrogen, for example, which is applied each year 
for the immediate crop, amounts to rather more than one-fourth 
of that applied for four years in the rotation experiments. 
Thefigures show that— without manure — there was much less 
dry matter in grain, straw, and total produce, in the crops grown 
continuously than in those grown in rotation ; in fact, in the 
total produce only about three-fifths as much. The much higher 
amount under rotation is quite consistent with the explanation 
that in the rotation experiments without manure, the roots 
having failed, the barley crop had, in point of fact, the benefit of 
the preparation which bare fallow is known to confer. 
With superphosphate alone, the continuously grown barley 
crops yielded more dry matter in grain, straw, and in total pro- 
duce, than those without manure ; the excess being largely due 
to increased capability of utilising the available nitrogen of the 
surface soil, under the influence of the phosphatic manure. Both 
sets of the superphosphate rotation crops yielded more dry matter 
than the continuous ones, the excess being, however, much less 
where the rotation roots had been removed than where they had 
been consumed or spread upon the land. The effect ofthe growth 
and accumulation by the previous root-crop, and of the more or 
less available manurial residue left under the different conditions, 
% 
as compared with the result when the barley is grown year after 
year on the same land, is thus very evident. 
As already said, the amount of nitrogen annually applied on 
the mixed manure plot was, for the continuous crops, somewhat 
more than one-fourth of that applied for the preceding root-crops 
in the case of the rotation plots. Under these circumstances, 
the amounts of dry matter in grain, straw, and total produce, 
were considerably less in the barley grown in rotation where the 
roots and leaves of the turnips had been removed than in that 
grown continuously ; but where in the case of the rotation barley 
the root-crops had been consumed or spread upon the land, the 
